Release of potassium sorbate from tapioca starch films

CONTE A., FLORES S., CAMPOS C., GERSCHENSON L., DEL NOBILE M.A.

Nápoles, Italia

Simposio; CIGR - Section VI - III International Symposium. Food and agricultural products: processing and innovations; 2007

Abstract In this work the release of potassium sorbate from tapioca starch-based edible films, with glycerol as plasticizer, was studied and mathematically modelled. Tapioca starch its an interesting polymeric matrix because its price is lower than starches from other sources. In order to describe the phenomena involved in the active compound release, the diffusion of water molecules into the polymeric film, the counter diffusion of the active compound and the swelling of the polymeric matrix, a semiempirical approach was proposed. The starch-based films were prepared by casting technique, using three methods: method 1 (slow gelatinization and slow dry), method 2 (rapid gelatinization and slow dry) method 3 (rapid gelatinization and rapid dry). Before testing, the obtained dried films were conditioned at 25º C, over saturated solution of NaBr (water activity, aW @ 0.575) for 7 days. Both kinetic of preservative release to a liquid medium and swelling kinetic were evaluated at pH 3 and 4. From the obtained results it can be inferred that the proposed model satisfactorily fits the experimental data allowing concluding that casting technique which produce films with high amorphous degree determines a greater contribution of matrix relaxation to sorbate release. This trend can be attributed to the increased influence of matrix relaxation on the water sorption kinetic. The pH of the receiving media contributed slightly to antimicrobial release and its effects seem to be related to the influence of this variable on antimicrobial solubility.